FI105564B - Superabsorbent polymer with improved absorption properties - Google Patents

Abstract

Super-absorbent polymers having superior dryness properties when incorporated into absorbent articles are made from acrylic acid and crosslinking agent polymerized under controlled conditions.

Description

x 105564

SUPER ABSORBING POLYMER WITH IMPROVED ABSORPTION PROPERTIES

The field of the invention is hydrogel-forming polymer compositions made from crosslinked polyacrylic acid.

Water-insoluble hydrogel-forming polymers capable of absorbing large amounts of water and aqueous liquids are well known compositions. Known as superabsorbent polymers, these polymers are slightly crosslinked acid-functional polymers that swell in aqueous liquids but do not dissolve therein. Superabsorbent polymers have been found to be particularly useful in diapers, women's hygiene products, and surgical blankets. Descriptions of superabsorbent polymers and their use can be found in U.S. Patent Nos. 3,669,103 and 3,670,731.

U.S. Patent No. 4,654,039 (reprint 20, 32,649) relates to hydrogel-forming polymeric compositions disclosed as substantially water-insoluble, slightly crosslinked, partially neutralized polymers derived from unsaturated, polymerizable acidic moiety and . These '·' polymers are prepared by polymerizing an acid monomer and a crosslinking monomer in water using a redox initiator system, followed by partial neutralization of the acid groups with sodium hydroxide and then drying and grinding the polymer to a powder.

British Patent No. 2,119,384 discloses superabsorbent polymers prepared by water polymerization of acrylic acid with sodium acrylate and a crosslinking monomer using a persulfate initiator 35, followed by drying and then heating with a crosslinking agent having at least two carboxylic acids. 2,105,664 functional groups reactive with wart groups.

In U.S. Patent No. 4,497,930, a superabsorbent polymer is prepared by polymerizing acrylic acid 5 by a reverse emulsion process followed by crosslinking the polymer with a diepoxide compound.

According to U.S. Patent No. 4,295,987, the superabsorbent polymer is prepared by polymerizing acrylic acid and multifunctional acrylate monomer 10 in water using a persulfate initiator, followed by neutralization of the acid groups with lye and then addition of a divalent cation salt, e.g. zinc acetate, to zinc acetate.

Numerous other patents disclose superabsorbent 15 buoyant polymers and their use, for example, U.S. Patents 4,076,663, 4,552,938, 4,550,438, 4,535,098, 4,820,773, and European Patent Application 189,163.

Over the years, many improvements have been made to the performance and properties of superabsorbent polymers, for example, gel strength and absorption capacity. However, the properties of these superabsorbent polymers are not balanced. Typically, polymers with a high modulus of elasticity have a reduced absorption capacity, resulting, for example, in inferior drought in the diaper. Polymers with high absorption capacity have low pressure absorption and reduced modulus of elasticity, which also worsens diaper dryness. EP-A-339 461 discloses absorbent products made using superabsorbent polymers having the ability to exert pressure; under.

There is a need to find a superabsorbent polymer with equilibrium properties which results in improved dryness and leakage of the sheet in the use of the 35 polymer sheath.

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The invention relates to superabsorbent polymers, i.e. hydrogel forming polymers. In one aspect, the invention relates to improved superabsorbent polymer compositions. In another aspect, biscuit-5 relates to polymers made from superabsorbent materials.

The superabsorbent polymer of the invention is prepared by forming an aqueous solution of acrylic acid, a crosslinking monomer which is a polyethylene-unsaturated polymerizable monomer, and optionally a hydroxy-containing polymer, by adding a redox initiator system and optionally a thermally free radical roads, maintaining at peak temperature to reduce the concentration of free monomer to less than 1000 ppm, neutralizing 50-100% of the acid groups of the resulting polymer with base, and optionally adding a multifunctional compound having at least two groups capable of forming with carboxylic acid groups, drying the polymer to a moisture content of less than 10% by weight and milling the dried polymer to a powder.

The superabsorbent poly-25 polymer according to the invention has the following properties:. absorbance at a pressure of at least 30 g / g; a reabsorption capacity of at least 40 g / g; modulus of elasticity not less than 9.0 x 10 * dynes / cm2, Recovery ratio not less than 85%.

The articles made from the polymer according to the invention have a dry value of at least 40.

"I. The primary monomer used in the preparation of the superabsorbent polymer of the invention is acrylic acid. The crosslinking monomer copolymerized with acrylic acid is a polyethyleneically unsaturated monomer having at least two polymerizable groups per molecule and soluble in water or acyl 10 10 646. examples of polymerizable groups are acrylic groups, methacrylic groups, allyl-groups and vinyl groups. Crosslinking are polyols, polyacrylic polyols polymetakryy-5 esters, polyallyl amines, polyallyl ethers, polyacrylamido, polymetakryyliamidoyhdis-making and divinyl compounds. Specific examples of sil-monomers are tetrallyloxyethane-allyloxyethane, n, n ' -methylenebisacrylamide, N, N, -methylenebismeth-10 acrylamide, triallylamine, trimethylolpropane triacrylate, glycerol propoxytricrylate, divinylbenzene and the like. at least two allyl groups, most preferably four allyl groups. The monomer of Edul-15 is tetraallyl oxyethane.

Optional components for use in preparing the superabsorbent polymers of the invention are water-soluble hydroxy-containing polymers, for example polysaccharides and vinyl or acrylic polymers. Examples of water-soluble polysaccharides are starches, water-soluble celluloses, and polygalactomannans. Suitable starches include natural starches, for example sweet potato starch, potato starch, wheat starch, corn starch, rice starch, tapioca starch and the like. Processed and modified starches, for example dialdehyde starch, alkyl etherated starch, allyl etherified starch, oxyalkylated starch, aminoethyl etherated starch and cyanoethyl etherated starch are also suitable.

Water-soluble * celluloses useful in the invention are obtained from wood, straw, yoke, seed flakes and the like, which are then converted to hydroxyalkyl cellulose, carboxymethyl cellulose, methyl cellulose and the like.

Suitable polygalactomannans include guar gum and locust bean gum (105564 gums) as well as their hydroxyalkyl, carboxyalkyl and aminoalkyl derivatives.

Water-soluble vinyl and acrylic polymers include polyvinyl alcohol and poly (hydroxyethyl 5 acrylate).

A preferred polysaccharide for use in the invention is natural starch, for example wheat starch, corn starch and alpha starch.

In the preparation of the superabsorbent polymer of the invention, the acrylic acid and the water-soluble polymer are reacted in an amount of about 90 to 100% by weight of acrylic acid, and in an amount of 0 to 10% by weight of water-soluble polymer. The amount of polyethylenically unsaturated crosslinking monomer may range from about 0.005 to 1.0 mole% based on moles of acrylic acid, and preferably from about 0.01 to 0.3 mole%.

The polymerization initiators used in the invention are redox initiators and optionally of the thermal type. Redox initiators are used to initiate and substantially complete the polymerization reaction. The thermal initiators, if used, are involved in ensuring that the content of 25 free monomers in the product is reduced to less than 1000 ppm by weight.

As far as redox initiators are concerned, any of the well-known water-soluble reducing agents and oxidizing agents may be used in the invention. Examples of reducing agents include compounds such as ascorbic acid, alkali metal sulfites, alkali metal bisulfites, ammonium sulfite, ammonium bisulfite, alkali metal hydrogen sulfite, ammonium hydrogen sulfite, ferrometallic salts, e.g. like.

β 105564

Oxidizing agents include compounds such as hydrogen peroxide, alkali metal persulfate, ammonium persulfate, alkyl hydroperoxides, peresters, diacrylic peroxides, silver salts and the like. Particularly preferred is its redox initiator pair ascorbic acid and hydrogen peroxide.

In order to obtain superabsorbent polymers having the superior properties claimed in the claims of the present invention, the reducing agent-10 must be used in an amount of about 2 x 10'5 to 2.0 x 10'2 mol% based on moles of acrylic acid. The amount of oxidizing agent used is from about 2.0 x 10 3 to about 1.1 mole% based on moles of acrylic acid.

In order to ensure complete polymerization of the acrylic acid monomer 15 and the crosslinking monomer, a thermal initiator may be included in the polymerization process. Useful thermal initiators include "azo" initiators, i.e. compounds containing the -N = N- structure. Any azo compound having some solubility in water or in an acrylic acid-water mixture having a half-life of 10 hours at or above 30 ° C may be used. Examples of useful azo initiators are 2,2'-azobis (amidinopropane) dihydrochloride, 4,4'-azobis (cyano valeric acid), 4,4'-butyl azocyano. valeric acid, 2,2'-azobis (isobutyronitrile) and the like. A preferred azo initiator for use in the invention is 2,2'-azobis (amidinopropane) dihydrochloride. The thermal initiators are used in an amount of 0 to about 1 to 30 mole% based on the weight of the acrylic acid.

The polymerization process for preparing the compositions of the invention is carried out in water with a solids content, i.e., an acrylic acid and water soluble polymer content of about 20 to 30 weight percent, with 35 weight percent based on the total weight of water, acrylic acid and water soluble polymer.

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The process for preparing the compositions of the invention is an adiabatic reaction which is initiated at a temperature of 5 to 20 ° C and the temperature rise of which does not exceed a peak temperature of 90 ° C.

Generally, the peak temperature is about 60-75 ° C. The time required to reach the peak temperature will vary depending on the monomer concentration, the amount of initiator and the special initiator used, as well as the size of the reaction charge and whether the reaction 10 is isolated or not. Usually the time is about 1-2 hours. When the peak temperature is reached, the temperature is maintained at about 10 ° C from the peak temperature and preferably at about 5 ° C for about 1-12 hours to ensure that the polymerization is complete and that the residual monomer content is less than 1000 ppm.

The carboxylic acid groups in the composition of the invention are neutralized with a base of about 50 to 100 mol%, preferably about 65 to 75 mol%. Preferred bases are alkali metal hydroxides, with sodium hydroxide being the most preferred base. Other bases may also be used, such as alkali metal tallow hydroxides, ammonium hydroxide, alkali metal, alkali metal and ammonium carbonates, bicarbonates and alcoholates, amines and the like.

·. The post-crosslinking compound which may be added to the reagents after the neutralization step may be any compound having at least two reactive moieties which may react or form a bond with the carboxylic acid or carboxylic acid salt groups and be substantially aqueous; soluble. Organic compounds containing epoxy groups, hydroxyl groups, amine groups, phenol groups or halohydrin groups are suitable for use.

Examples of useful post-crosslinking compounds include ethylene glycol diglycidyl ether, epichlorohydrin, glycerol, ethylenediamine, bisphenol A and the like. A preferred post-crosslinking compound is ethylene glycol diglycidyl ether.

The crosslinking compound is added to the poly-5 polymer in an amount of 0 to about 1.8 mol% based on moles of acrylic acid, and preferably, the crosslinking compound being diglycidyl ether, about 0.02 to 0.15 mol%.

As stated above, the polymerization reaction is an adiabatic reaction which is carried out without any external heating. The monomers, i.e., acrylic acid, crosslinking monomer and polysaccharide, if used, are dissolved in water in the reactor. The dissolved oxygen is removed from the solution by a stream of inert gas, e.g. nitrogen, and the temperature is lowered to about 5-20 ° C. Polymer-15 roaming initiators, i.e., a thermal initiator, if used, are added to the reactor with thorough mixing and reduction. After a brief induction step, polymerization begins, as indicated by the increase in temperature. The peak temperature is reached in about 1 -2 0 3 hours. Generally, the peak temperature is about 60-75 ° C. Once the peak temperature is reached, the polymer is kept in a thermally insulated container (which may be a reactor) for a sufficient period of time to complete polymerization, as indicated by a reduced monomer concentration below 1000 ppm. Usually this time is around 2-12 ·: hours.

When the polymerization reaction is complete, the polymer gel is removed and broken down into small particles. The aqueous base is then added to neutralize some or all of the acid groups. The gel is cleaved again to ensure uniform mixing of the base I with the polymer. The aqueous solution of the post-crosslinking agent can then be added and the gel re-cleaved to ensure uniform mixing. The Gee-35 1 is then heated at a temperature of about 20 to 200 ° C to enhance the reaction between the curing agent and the carboxylic acid groups and to dry the polymer to a moisture content of about 10% by weight. The dried polymer is then milled and screened to a particle size of about 20 to 400 mesh using a U.S. standard sieve, with a preferred size of 20 to 200 mesh, and most preferably 95% of the particles having a size of 20 to 140 mesh.

A template sheath was used to evaluate the properties of the superabsorbent polymer. The diaper was constructed of a layer (14 x 37 cm) of pulp having a basis weight of 200 g / m 2 and a nonvowe backing sheet. The supe-10 adsorbent polymer, 5 g, was then applied as uniformly as possible to the pulp layer. The polymer was then covered with a layer of cellulose (14 x 37 cm) having a basis weight of 100 g / m 2 and a nonwoven surface sheet.

Testing of the model diaper was carried out as follows: 1) 50 ml of 0.9% saline was poured into the center of the diaper every 5 minutes until a total of 150 ml was used; 2) 5 minutes and 2 hours after the final addition of saline solution, 10 trained persons assessed the dryness of the diaper by touching the diaper and each rated it 1-5 for each time interval. The significance of the grades was: 5 - completely dry 25 4 - slightly damp 3 - damp 2 - slightly wet 1 - completely wet 3) The scores for each individual were summed over 30 time periods. The lowest grade in the above test was 10 and the highest grade 50. The I. grade for diapers using the superabsorbent polymers of the invention was at least • 40.

The superabsorbent polymers of the invention were also evaluated in the following experiments.

1) Absorbance at 10 105564

The test determines the absorptive capacity of a superabsorbent polymer at a pressure of 20 g / cm 2 (e.g., a child sitting).

2) Re-absorption capacity The assay determines the absorption capacity of a super-absorbent polymer after it has been partially hydrogenated (10 g / g at a salt content) and shear stressed a total of 50 times at 22 g / cm 2 (i.e. slightly wet jacket is subjected to sleeping or sitting stress).

10 3) Elasticity module

The test determines the retention capacity of the superabsorbent polymer when fully impregnated to prevent structure breakdown and fluid loss (i.e., the child sits wet with a diaper).

15 4) Recovery rate

The test determines the resorbability of the superabsorbent polymer after repeated pressures.

Absorbance under pressure is measured using an automatic absorber tester, model KM 350 (Kyowa Seiko Co., Ltd) and a plastic tube with an inner diameter of 25 mm and a length of 50 mm with a metal mesh (100 mesh) at the bottom. Samples from 32 to 100 mesh are used in the test.

25 Test sample, 0,100 ± 0,01 g, place in a plastic tube and spread evenly over a metal screen. Weigh 100 g on the sample. The plastic tube is placed in the center of the porous plate of the tester with a container containing saline (0.90 w / v% NaCl-30 in water) under the plate. 1 hour after absorption, the volume of saline absorbed is determined (a ml). Blood test * is performed using the same procedure without superabsorbent polymer (b ml). The absorbance at pressure is equal to (a - b) x 10.

35 The reabsorption capacity is determined as follows: A test sample, 1.00 g, is placed in a beaker containing 10.0 g of saline (0.9% w / v aqueous NaCl-105564) and left for an hour to obtain a smooth gel. The gel is then placed in a polyethylene bag which is sealed after the air has been evacuated. The gel-containing pouch is placed on a press-5 blade and cut under the following conditions:

Roll weight: 1 kg

Rolling speed: 1 min / rev

Coding frequency: 50 times

Shear loading weight: 22 g / cm 2 The gel's reabsorption capacity is then determined for 1.10 g of sheared gel placed in a plastic tube using the method described under absorbance pressure, except that 100 g is not used.

The modulus of elasticity was determined as follows: a test sample, 0.50 g, was placed in a beaker containing 25.0 g of synthetic urine (aqueous solution containing 0.8 wt% NaCl, 2.0 wt% urea, 0.08 wt% MgSO 4 · 7H 2 O, 0.03% by weight CaCl 2, wt.% Of the weight of the solution) and left for 1-3 hours to obtain a smooth gel. A portion of the gel, 0.2 ± 0.01 g, was then placed on a crawler, model RE 3305 (Yama-den Co., Ltd.), and the deformation resistance was measured at a constant load of 15 g / cm 2.

25 Elastic modulus in dyne / cm2 calculate · ·. was determined from the ratio of unit stress to unit deformation.

The recovery ratio was determined using the creep-30 story and synthetic urine presented in connection with the modulus of elasticity. In the recovery ratio test, 0.3 g of superabsorbent polymer was added to 15 g of synthetic urine in a plastic bottle. The flask was sealed, shaken and allowed to stand for 1 hour to obtain a smooth gel. A portion of the gelled sample, 0.1 g, was placed in a crawler and the elasticity of the gel was measured with a probe upon impacting the table and sample 20 times. The recovery ratio was calculated as 12 to 105564 as the ratio of polymer height at end / polymer height at start x 100.

The following examples illustrate the invention in detail. Parts and percentages are by weight and 5%, unless otherwise stated.

Example

800 parts of acrylic acid, 4.0 parts of tetra-10 allyloxyethane, 300 parts of 8% oxidized starch in water and 2,899.5 parts of water were added to the unheated / isolated reactor. Nitrogen was bubbled through the solution and the temperature lowered to 10 ° C. When the dissolved oxygen content was less than 1 ppm, the following initiators in the listed order were added: 0.8 parts of 2,2-azobisamidopropane dihydrochloride in 10 parts of water; 0.008 parts ascorbic acid; 0.23 parts of 35% hydrogen peroxide.

After an induction period of 20 minutes, the polymerization started and the peak temperature of 60 ° C was reached within 2 hours. The product gel was kept in the isolated reactor for a further 2 hours, at which time the residual monomer content decreased to less than 1000 ppm.

After the polymer gel had been cleaved ·. in a meat grinder, 644.38 parts of a 50% sodium hydroxide solution in water were added thereto. The gel temperature was about 60 ° C before the lye addition and the temperature of the lye solution was 38 ° C. The gel was re-digested to mix with a basic solution for uniform neutralization. 0.8 parts of ethylene glycol diglycidyl ether were then added to the gel, the temperature of which had risen to 88-93 ° C, at a temperature of 24 ° C. The gel was cleaved three times three times to distribute the crosslinker evenly. The polymer was then dried to a moisture content of 10% on a rotary type tumble dryer heated at 100 psi steam. The resulting polymeric flakes were ground and screened to a particle size of 20-400 mesh (US standard sieve). The polymer had the following properties: Absorbance at pressure (AP) - 30 g / g

Re-absorption Capacity (Re-Abs. Capacity) - 42 g / g Elasticity Module (Elast. Mod.) - 9.3 x 104 dynes / cm2 Recovery rate - 86%

Model diaper - 5 minutes - 43 10 2 hours - 43

Comparative Example

The polymers used in commercial diapers were tested and compared with the polymers of the invention. The results of the tests are shown below:

Polymer Drought AP Ref. Elast. mod.

abs.

_____ Cap .__ __5 min 2 h g / g g / g 104 dyne / cm2

Luvs Deluxe__36__38 27 20 11.8_

Ultra Pampers Plus 3 7__37 26 26__13,1_

Ultra Pampers__34 36 23 28__9,9_

Snuggums Ultra__34__38 24 29 8.4_ i. Regular Pampers__31__33 25 23 12.7_

Huggies Supertrim 31__35 21 31__7.8_

Thick Pampers Plus 2 9__33 25 27 8.6_ SANWET® IM-1500 30 38 12 38 7.4_ SANWET® IM-10 0 0 22__35 3 10 4.7_

Invention__43__43 30 42__9,3_ * * ι «

The superabsorbent polymers of the invention are useful in the manufacture of moisture-absorbing products, such as disposable diapers, sanitary napkins, incontinence pads, bandages and the like. The superabsorbent compositions of the invention are particularly useful for the manufacture of thin, ultra-thin disposable diapers having excellent moisture absorption capacity and reduced flowability due to their balance of properties above.

In the manufacture of absorbent products from the compositions of the invention, the superabsorbent composition is mixed or dispersed in a porous fiber matrix. The matrix is made of wood pulp or fluff, cotton linters, melt blown synthetic fibers, or a blend of melt blown fibers and wood flakes. The synthetic fibers may be polyethylene, polypropylene, polyesters, polyester or polyamide copolymers or the like.

Absorbent products, such as disposable diapers, are made of a liquid impermeable backing material, a fluid permeable body-facing surface material, and a fluid-absorbing composite layer between the backing material and the surface material. The liquid impermeable backing material may be made from commercial polyolefin film and the liquid impermeable backing material may be made from commercial non-woven material, such as spunbond or braided nonwoven, which is water-repellent and capable of penetrating ·. uriinin.

The superabsorbent polymers of the invention can be used in the manufacture of absorbent materials, for example those disclosed in U.S. Patent Nos. 3,669,103, 3,670,731, 4,654,039, 4,699,823, 4,430,086, 4,973,325, 4,892,598, 4,798. 603, 4,500 1,315, 4,596,567, 4,676,784, 4,938,756, 4,537,590, 4,935,022, 4,673,402 and EP 397,110, 378,247 and 339,461, all of which are incorporated by reference.

35 The capacity of products made from flocculating and superabsorbent polymers to absorb repeated doses of liquid is determined as follows: 15) 1) An absorbent pad is formed comprising about 2 g of absorbent polymer and about 12 g of charcoal and compressed to a density of about 0.2 g / cm3 about 6 inches.

2) 30 ml of 0.9% w / w saline is then added to the absorbent pad. After 20 minutes, place 25 g and 11 cm filter paper on the cushion and apply enough weight to apply a force of about 1 psi to the cushion. The filter-10 tin paper is then weighed. Re-dispense 30 ml of saline into the pad and after 25 minutes use filter paper and weight as above and weigh the filter paper. The test is then repeated a third time. The rewet response is calculated as 15: wet weight of filter paper - dry weight of filter paper = rewet response

The re-utilization response of the superabsorbent polymer of the invention, polymer A, and another polymer B having somewhat lower properties as well as the properties of polymers A and B are shown in the following tables.

Table 1 2 5 _____. Polymer AP Nov.abs. Elast.mod. Feedback Ratio ___ Cap .___ A_ 30 42_ 9.3 x 104 86% _ B_ 29 39_ [8.8 X 104 [83% _ u 1 ««

Table 2 16 105564 _Water Wetting Response of Polymer A____ Flow-Polymer 1st Dose 2nd Dose 3rd Dose Weight Weight____ 9_ 0.8__0_ 11.3_22,5_ 6_ 1,6__0_ 5.2 16,9_ 12_J__0__4_j_6__11,1 _ _9___0_ 3, 3_ 8,0 _ _6__3_j_2_ 0__lj_9_ 3,6_ 12__3_j_2__0_ 3,6__4 ^ 8_ _9_1 4,0_ [0_ [2,8_I 4,6_ _ Polymer B Rehydration Response_ Fluff Polymer 1st Dose 2nd Dose 3rd Dose Weight Weight_____ ___ ^ _8__0__12,5,5 22,4 _6__1 _; _ 6__0__7 ^ 2__18,4_ 12__1 ^ 6__0_ 5,8__12,4_ 9_2,4__0_ 3,8_ 8,8_ _6_ 3,2__0__1 ^ 6_ 4,8_ 12_ 3j_2__0_4,5__5_j_9_ 9_ [4,0_lO_ [ 3,0_ [5,6_

As can be seen, both superab-5 sorbent polymers had a re-wetting response of 0 after one dose. After the second and third doses, the overall response of the products of the superabsorbent polymers of the invention to re-wetting was superior, i.e., lower than that of the products of the other polymers.

The principle, preferred embodiments and operating models of the invention are set forth in the preceding description. However, the invention, which is intended to be protected by the application, is not intended to be limited to the actual forms shown, but is intended to be illustrative rather than limiting. Those skilled in the art can make modifications and changes without departing from the spirit of the invention.

Claims (13)

A superabsorbent polymer, characterized in that it comprises a copolymer formed from an acrylic acid, a multifunctional monomer and a water-soluble hydroxyl-containing polymer, wherein the multifunctional monomer contains at least 2 ethylenically unsaturated groups per molecule and the amount of the same is approx. 0.005 - 1.0 mol% calculated on the mole amount of acrylic acid and wherein 0-10% by weight of water-soluble hydroxyl-containing polymer is calculated on the weight of the acrylic acid and the water-soluble polymer, and wherein 50 - 100% of the carboxylic acid groups of the copolymer are neutralized by a basic aqueous solution and the copolymer is post-crosslinked with a multifunctional compound, of which about 15 are present. 0 - 1.8 mole% calculated on the mole amount of acrylic acid, the absorbance of the superabsorbent polymer under pressure being at least 30 g / g, the re-absorbing capacity at least 40 g / g, the modulus of elasticity at least 9.0 x 10 4 dyne / cm 2 and the recovery ratio is at least 85 20%. 2. Polymer according to claim 1, characterized in that the ethylenically unsaturated groups of the multifunctional monomer are allyl groups. Polymer according to claim 2, characterized in that the multifunctional monomer is tetra-allyloxyethane. 4. Polymer according to claim 3, characterized in that there are approx. 0.01 - 0.3 mol% tetra-allyloxyethane. 3 0 5. Polymer according to claim 1, characterized in that the multifunctional monomer is: a) N, Ν'-methylene bisacrylamide, b) trimethylolpropane triacrylate, c) glycerol propoxy triacrylate or, d) divinylbenzene. 2i 105564 Polymer according to claim 1, characterized in that the water-soluble hydroxyl-containing polymer is a polysaccharide. 7. Polymer according to claim 6, characterized in that the polysaccharide is a natural starch. 8. Polymer according to claim 1, characterized in that the particle size of the polymer is such that 95% by weight of the particles are between 20 - 10 140 mesh (US standard seals). Polymer according to claim 1, characterized in that the cross-linking multifunctional compound is a polyglycidyl ether of a polyol. Polymer according to Claim 9, characterized in that the polyglycidyl ether is diglycyldyl ether of diethylene glycol. 11. An absorbent product, characterized in that it comprises a porous fiber matrix wherein the polymer of claim 1 is dispersed. Absorbent product according to claim 11, characterized in that the porous matrix is placed between a liquid impermeable material and a liquid permeable material. Absorbent product according to claim 11, characterized in that 5 to 100% by weight of absorbent polymer is calculated on the fiber.